Rotary tube furnace



March 27, 1956 c. s. RANKIN ROTARY TUBE FURNACE Filed Nov. 13, 1951 Z a x Z w 2 4 8 0 3 3 23 xRN 7 6 m u/V F/GJ.

INVENTOR. CLARENCE S. RANK/N A T TORNE Y United States Patent ROTARY TUBE FURNACE Clarence S. Rankin, San Francisco, Calif., assignor to Pacific Foundry Company, Ltd., San Francisco, Calif., a corporation of California Application November 13, 1951, Serial No. 255,970

Claims. (Cl. 263-33) This invention is concerned with rotary tube furnaces and particularly furnaces in which the rotary tube is heated so highly that it tends to distort transversely to its axis of rotation. The furnace of the invention has general utility, but is particularly useful for operations involving the use or production of explosive or poisonous gases in the tube of the furnace, so that the tube must be sealed from the atmosphere. By way of example, the furnace is useful in the production of metal powders from metal oxides and other compounds by reduction.

with hydrogen.

In accordance with the invention, two chambers are located at the ends of the rotary tube and each of the chambers is provided with a sealed hearing which is affixed to the inside of the chamber. The two ends of the rotary tube are rotatably mounted in the two sealed bearings which permit some longitudinal movement of the rotary tube, i. e. such movement as may be caused by thermal expansion and contraction of the tube. The bearings have a liquid seal arrangement wherein a liquid, such as liquid grease, is retained, for example by packing and annular retaining rings. A space through which air may circulate may be provided between the sealed bearing and the rotary tube so that the liquid in the seal will not become too hot.

The two chambers communicate with flexible conduits through which the solids to be treated may be introduced to the rotary tube and the treated substance removed. Resilient mounting means is provided for each of the chambers for permitting limited movement of the chambers in planes tranverse to the axis of the tube, so that the seals between the rotary tube and the two chambers will not be destroyed if the rotary tube becomes distorted transversely to its axis of rotation.

The invention is explained with reference to the companying drawings, in which:

Fig. 1 is an elevation, partially in section, of a preferred form of the furnace; and

Fig. 2 is a sectional view along line 22 of Fig. 1.

Solids to be treated, say pulverized metal oxide, are introduced through a feed funnel which is connected to a feed hopper 12 through a shut-off valve 14. A pair of valves 16 and 18 are provided for sweeping air from the hopper by means of an inert gas.

A work shelf 20 is located around the hopper, and a screw feeder 22 is located at the base of the hopper. The feeder is rotated by means of a sprocket 24 connected to a suitable source of power (not shown).

The screw feeder communicates with a tube 26 through a disconnect flange 28 and a shut-off valve 30.

The hopper and the tube 26 are rigidly supported by means of the frame 32. A bellows 34 provides a flexible, gas-tight connection between the tube 26 and an inlet or feed tube 36 which is rigidly secured to a chamber at the head of the rotary tube furnace, thereby permitting limited movement of the tube 36 with respect to the stationary feeder apparatus without permitting air to enter or gas the two chambers.

ice

to escape from either the feeder apparatus or the rotary tube of the furnace.

The furnace comprises an inclined rotary tube 38 which is composed of a central tube 40 provided with lifters 42 for stirring the solids undergoing treatment, and a pair of end tubes 44 and 46 by which the rotary tube ararngement is supported. A firebox 48, containing a plurality of burners 50, surrounds the central portion 40 of the rotary tube 38.

A chamber 52 is located around the inlet end of the rotary tube 38, and the inlet tube 36, which extends through the chamber 52 and into the end of the portion 44 of the rotary tube, is welded to the wall of the chamber 52 so as to provide a gas-tight seal.

Another chamber 54 is located around the outlet end of the rotary tube 38, and the chamber 54 communicates with a receiving box 56 through a disconnect flange 58, a shut-off valve 60, another disconnect flange 61 and a bellows 62. The arrangement of the bellows 62 is similar to that of the bellows 34, and it provides a flexible gas:

tight connection between the chamber 54 and the receiving box 56, thereby permitting limited movement of the rotary tube of the furnace and the chamber 54 with respect to the stationary receiving box 56.

Valves 63 and 63A are provided in the receiving box and removing hydrogen or other reactive gas from the rotary tube 38.

The ends 44 and 46 of the rotary tube 38 extend inside the chambers 52 and 54, and gas-tight seals 70 and 70' are provided between the ends of the rotary tube and The chambers are provided with resilient mountings 72 and 72' which permit limited movement of the chambers in a plane transverse to the axis of the rotary tube.

are the same type, only the structure of the seal 70 and the mounting 72 will be described.

A cylindrical tube 74 is located around the end of the tube 46 and is rigidly secured thereto by a gas-tight member 76 atone end and by a member 78 at the other end which permits air to enter the space between the tubes 46 and 74.

A gas-tight connection is made between the chamber 54 and the tube 74 by means of a liquid seal containing a heavy liquid grease which is inert to hydrogen. The grease is confined in a lantern ring 80 which is held in place by two sets of packing 81 located between a fixed metallic ring 82 and an adjustable metallic ring 84. A plurality of bolts 86 are provided for adjusting the position of the ring 84. A pressure gun 88 is provided for introducing the grease to the lantern ring and for maintaining the grease under pressure. The seal 70 is cooled by means of the air space between the tubes 46 and 74, so that the grease will not be destroyed by the heat of the tube 46. Thus, the seal 70 permits both rotary and limited longitudinal'movement of the tube 38 without allowing air to enter the chamber 54 or gas to escape from I The support 72 for the chamber 54 comprises two arms 90 and 92, which are attached to the outer periphery of the chamber, four springs 94 to 97, and two upright rods and 102 which are rigidly attached to the supporting frame for the furnace. The rods 100 and 102 extend through holes in the arms 90 and 92. These holes are larger than the rods so as to permit limited horizontal movement of the arms 90 and 92 transverse to the axis Patented Mar. 27, 1956 Valves 66 and 67 are of the rotary tube 38. The springs 94 to 97 permit limited rotary movement of the arms 90 and 91 about the axis of the rotary tube 38. Thus, limited movement of the chamber 54 is permitted in a plane transverse to the axis of rotation of the tube 38.

A pair of trunnions 116 and 112 are provided for supporting the ends 44 and 46 of the rotary tube 38, the trunnion 110 being driven by means of a sprocket 114 which may be coupled to a suitable source of power (not shown). The trunnion 112 is provided with a wheel 115 which serves to support the thrust of the rotary tube to ward the lower or tail end of the tube.

In an operation for which the furnace of the invention is particularly suitable, the fire box and the rotarytu'be are brought up to operating temperature while the tube is revolving. The feed hopper is filled with finely divided metallic oxide to be reduced; the valves 14, 30 are closed; and the hopper is swept out with an inert gas which is introduced and removed through the valves 16, 18. The rotary tube and the receiving box 56 are then swept out with an inert gas which is introduced through valves 63', 64 and removed through the valves 63A, 65. Then hydrogen is admitted through the valve 66 and removed through the valve 67.

The valve 30 is opened and the feeder 22 is started so that the metallic oxide is fed through the feed tube assembly into the rotating reduction tube 38, where it is heated. In passing through the rotary tube 38, both the hydrogen and the oxides are heated to a temperature at which partial or complete reduction of the oxides occurs but without substantial fusion. The end products of the reaction are finely divided particles, at least partially re duced to metal, and water vapor.

The reduced material passes through the chamber 54 into the receiving box 56. When-the receiving box is full, the valve 60 is closed and the receiving box is dis connected at the flange 61. The receiving box is emptied and then reconnected to the flange 61 and swept out with an inert gas. The valve 60 is then opened and the receiving box will again start to fill. There is sufiicient storage capacity in the chamber 54 to allow the furnace to run continuously provided the receiving box is emptiedpromptly.

The furnace tube should be maintained at a positive pressure at all times during operation to prevent air from leaking into the system and forming an explosive mixture. The seals prevent the escape of hydrogen from the system and thus prevent exterior formation of an explosive mixture, etc.

Even though the rotary tube 38 is heated so highly that it tends to distort transversely to its axis of rotation, none of the gas-tight seals are broken, because the chambers 52, '54 are supported so that they can move in a plane transverse to the axis of rotation of the tube 38. The liquid seals 70 and 79- permit both rotary and limited longitudinal movement of the tube 38 Without allowing air to enter the chambers 52 and 54. The inlet and outlet feed assemblies for the chambers 52 and 54 are somewhat flexible due to the metal bellows 34 and 62 so that their gas-tight seals are not broken when the chambers 52 and 54 move.

I claim:

1. In a furnace including a tube, means for rotating the tube on its axis, and means for heating the tube, the combination which comprises a chamber disposed around oneend of the tube, a sealed bearing adjacent the chamber wall with the rotatable tube mounted within it, resilient and permitting limited movement of the chamber .in .a.

plane transverse to the axis of the tube, and a flexible conduit attached to the chamber.

2. In a furnace including a tube, means for rotating the tube on its axis, and means for heating the tube, the combination which comprises a chamber disposed around one end of the tube, a sealed bearing adjacent the chamber wall with the rotatable tube mounted within it, a hollow cooling jacket mounted on the tube within the bearing and rotatable with the tube, resilient mounting means attached to and supporting the chamber and permitting limited movement of the chamber in a plane transverse to the axis of the tube, and a flexible conduit attached to the chamber.

3. In a furnace including a tube, means for rotating the tube on its axis, and means for heating the tube, the combination which comprises a chamber disposed around one end of the tube, a sealed bearing adjacent the chamber wall with the rotatable tube mounted within it, a hollow annular cooling jacket mounted on the tube within the bearing and rotatable with the tube but open at one end to the atmosphere, resilient mounting means attached to and supporting the chamber and permitting limited movement of the chamber in a plane transverse to the axis of the tube, and a flexible conduit attached to the chamber.

4. In a furnace including a tube, means for'rotating the tube on its axis, and means for heating the tube, the combination which comprises a chamber disposed around oneend of the tube, a sealed bearing adjacent the chamber wall with the rotatable tube mounted within it, resilient mounting means attached to and supporting the chamber and permitting limited movement of the chamber in a plane transverse to the axis of the tube, and a flexible inlet conduit attached to the chamber and entering it from above and projecting into the end of the tube.

5. In -a furnace including a tube, means for rotating the tube-on its axis, and means for heating the tube, the combination which comprises a chamber disposed around one end of the tube, a sealed bearing adjacent the chamber wall with the rotatable tube mounted within it, resilient mounting means attached to and supporting the chamber and permitting limited movement of the chamber in a plane transverse to the axis of the tube, a flexible inlet conduit attached to the chamber and entering it from above and projecting into the end of the tube, and an annular dam around the end of the tube for retaining in the tube material introduced into it through the inlet conduit.

References Cited in the file of this patent UNITED STATES PATENTS 997,381 Fasting July 11, 1911 1,434,796 Sellers Nov; 7, 1922 1,449,197 Russell -Mar. 20, 1923 1,535,209 Dubbs Apr. 28, 1925 1,930,756 Heath et al. Oct. 17, 1933 2,057,099 Ingraham Oct. 13, 1936 2,063,368 De 'La Roza, Sr Dec. 8, 1936 2,119,528 Doback et al. June 7, 1938 2,314,836 Seil Mar. 23, 1943 2,438,234 Stewart Mar. 23, 1948 2,444,868 Allen et al. July 6, 1948 2,455,539 Wahl Dec. 7, 1948 FOREIGN PATENTS 293,797 Germany Aug. 28, 1916 

